Monoliths of Tio2-SiO2: synthesis, characterization and photocatalytic activity

Monoliths of TiO2-SiO2 were synthesized by the Evaporation-Induced Self-Assembly (EISA) method and tested in the photocatalytic degradation of 4-chlorophenol. The way of adding the titanium precursor and the calcination conditions (temperature and air flow) were studied and were found to be key parameters in determining the physical, morphological, structural and photocatalytic properties. Opaque monoliths with crystalline anatase and rutile structures were obtained after calcination when the titanium precursor was directly added during the Si sol synhesis. Under another approach, adding the titanium precursor as a Ti sol to the Si sol, transparent materials with amorphous or small crystal size structures were produced. All monoliths presented mesoporous structures with specific surface areas in the value range of 528–813 m2g−1. The highest values corresponded to those materials calcined under air flow. The materials were tested in the 4-chlorophenol photocatalytic activity. After testing, a significant decrease in the concentration of 4-chlorophenol after 10 min of reaction was observed. The material in which the Ti precursor was added as sol (labeled as TSINS), presented the highest 4-chlorophenol degradation, reducing 86% of the initial concentration (2.33 × 10–4 mmol/cm3). Liquid chromatography shows the formation of intermediate compounds resulting from the decomposition of 4-chlorophenol and their subsequent partial mineralization.